Spicamycin (SPM) is an antitumor antibiotic produced by the bacterium Streptomyces alanosinicus 879-MT3 (Hayakawa et al., Agric. Biol. Chem. 49:2685-2691, 1985). Spicamycin and its derivatives are also used for pain relief (U.S. Pat. No. 5,905,069). Naturally occurring SPM has the following general structure, varying solely in the fatty acid moiety:
Synthetic variants of spicamycin and their use as an antitumor agent are described in Otake et al., U.S. Pat. Nos. 5,461,036 and 5,631,238.